16 CLASSIFICATION. 



CUMA. Shell pyriform ; spire elevated, acute, whorls angular or spinose ; 

 aperture oval-oblong ; columella convex, sometimes with a strong an- 

 gular tubercle in the middle ; outer lip acute, grooved internally. 



RAPANA. Shell veutricose, axis perforated to the apex ; spire de- 

 pressed ; aperture oval, narrowed anteriorly ; canal open, slightly 

 recurved; inner lip reflected, free anteriorly; umbilicus wide, corrugated. 



RHIZOCHILUS. Shell when young free, resembling Rapana ; when 

 adult, sometimes with more or less irregular solid shelly extensions of 

 the outer and inner lips, which clasp the axis of coral or the surface of 

 neighboring shells, and at length close the month with the exception of 

 the anterior siphonal canal which is converted into a shelly tube. No 

 operculum. (?) 



SEPARATISTA. Shell turbinate, subdiscoidal, the first whorls con- 

 tiguous, the last more or less separated ; aperture expanded, slightly 

 angulated, the margin everted; umbilicus very wide, infundibulifonn 

 with the whorls visible to the apex. No operculum. 



MELAPIUM. Shell ovate-pyriform, ventricose, imperforate, porcella- 

 nous ; spire very short, apex papillary ; aperture expanded, inner lip 

 with a thick, smooth callus at the hind part, columella twisted anter- 

 iorly, with a prominent oblique plait ; canal wide, recurved, directed 

 towards the left. Operculum unknown. 



WHITNEYA. A cretaceous fossil possibly synonymous with Melapium. 



RAPA. Shell thin, globosely pyriform ; axis perforate ; umbilicus partly 

 concealed by the reflected inner lip ; spire obtuse ; aperture oblong, 

 produced anteriorly into a wide, subrecurved canal. Operculum 

 unknown. 



MAGILUS. Shell when young, spiral, thin ; when adult, white, solid, 

 tubular, spiral for three or four whorls, the last prolonged into an 

 irregular straight or flexuous tube, solid posteriorly, and with a siphonal 

 keel on the left side. Operculum ovate, nucleus sublateral. 



MAGILINA. Young shell free, formed of a single whorl ; finally 

 prolonged into a tube which is attached by one side to the surface of 

 submarine bodies. 



NISEA. Shell composed of a discoidal portion and of two tubes ; the 

 last whorl recurved upon itself in the same way as Anastoma, in two 

 tubes of variable length and less sinuous than the single tube of 

 Magilus. (Fossil.) Relationships very doubtful. 



